Short span bridges in the U.S. that are located near rivers and streams typically use sheet piles to protect the abutmentagainst erosion and scour. In such bridges, the abutment axial load demands are usually carried by driven piles installed behind the scour protection sheet piles. An alternative bridge abutment design approach, successfully used for decades in Europe and in some projects in the U.S., involves installing sheet piles for the double function of scour protection and axial load bearing. This design paradigm shift has the potential to significantly reduce construction cost. However, widespread implementation and acceptance of this design approach requires full-scale axial load tests on instrumented sheet piles. This report describes and presents results of a research project funded by NCDOT to investigate the axial load capacity of sheet pile foundations. The project encompassed two test programs involving full-scale instrumented test piles. The first test program involved axial load tests under controlled conditions (e.g., controlled soil backfill, detailed geotechnical characterization, etc.) performed at a geotechnical test pit at UNC Charlotte. The second test program involved axial load tests at a field test site that allowed comparison of the axial stiffness and load capacity of a sheet pile wall and an H-pile. The second test program involved geotechnical conditions that are similar to those encountered in NCDOT bridge abutments in the Piedmont region. Additionally the project involved the assessment of the suitability of analysis and design procedures commonly used in practice for conventional deep foundations to the case of axially loaded sheet pile walls. The project also evaluated potential cost savings through a short parametric analysis that studied the axial load capacities of different abutment design configurations and the associated material costs for each design configuration.
Based on the research findings, the axial load capacity and axial stiffness of the sheet pile walls were found to be comparable to the values measured for H-piles installed under similar conditions and dimensions. Therefore, there is strong potential for incorporating the axial load bearing capacity of sheet piles for abutment bridge design that could result in substantial savings in terms of time and money.
